posi ?

what is a posi rear? I don't know much and I hear it alot, but I don't actually know what it is, or how the different size gears help. Could someone explain this for me?

Basicly speaking when you have a positive traction rear end that means that when your car starts to loose traction with one wheel then it puts traction to BOTH back wheels at the same time. My 96 TA has a posi track and when I punch it from a stop both rear wheels/tires lay rubber. It also likes to get sideways in the road if your not careful. The advantage is of course...better traction from a stop. A side advantage is if it don't start sliding you get better traction in the snow and wet too. Hope this helps a bit. I don't know a lot about the gears but this can change the ratio so that your car might be quicker with one rear end gear ratio than another that might make your car go faster on top end.
Rob

He explained posi well.

the gears are well, for different uses.

For example, a 4x4 jeep made for offroading may use 4.10 or higher. higher the gear, less top speed, more acceleration and low end power
a dump truck, same thing, high gear
a 6000 hp funny car, obviously a low gear.

understand? it also affects gas mileage. if your car had 2.73's and you got 40 mpg on the highway, now you swich to 3.73's and youll get maybe 30. this is because of the rpm's in top gear. with 2.73's say your rpm in top gear (overdrive in most cars) is 2000, with the 3.73's it will be more like 3000. therefor burning that much more fuel.

where exactly could you go to buy a posi... would jegs have it? and what kind of price range is it in?

very helpful, thanks

anyone here know if i have 2 series or 3 series carrier in my 98 Trans AM automatic. 2 series has 2.73 gear and 3 series has 3.23 gear stock. at 60 mph cruising my rpm are at about 1700 so maybe that would give you some idea

anyone here know if i have 2 series or 3 series carrier in my 98 Trans AM automatic. 2 series has 2.73 gear and 3 series has 3.23 gear stock. at 60 mph cruising my rpm are at about 1700 so maybe that would give you some idea

Ummm Make sure the car is NOT in over drive (you would have about 1.48 gear ratio) ;)

this should help you out...
http://www.dodgecharger.net/tech/RPM-Speed-Horsepower-Calculator.html

how exactly would my car not be in overdrive its and automatic and theres no over drive on or off mode
also what is the width of 98 trans am tires

You should have "P R N D 3 2 1" ON your SHIFTER"or maybe a "D" with a circle"O" around it and a plain "D"---3 or plain D is 1:1 ratio while the O-D is overdrive -You need diamter of tire not the width R16 or R17 =16' or 17'

Hope that clears it up - post w/any more questions

ok so i did it in gear 3 instead of D cuz i dont have the O-D and crusin at 60 mph my rpm was at 2400. im still not sure what my diameter of my tire is so i just put in 20 and that gave me 2.81 gear. so im assuming i got the 2.73

ok so i did it in gear 3 instead of D cuz i dont have the O-D and crusin at 60 mph my rpm was at 2400. im still not sure what my diameter of my tire is so i just put in 20 and that gave me 2.81 gear. so im assuming i got the 2.73

http://www.dodgecharger.net/tech/RPM-Speed-Horsepower-Calculator.html

go to that page and enter the number from your tire side wall such as
"195 60 R16" To calculate you diameter- its half way up the page...
Calculate Tire Diameter
Tire width - Series - Wheel Diameter
Example 275 - 60 R 15
Tire Width
Tire Series
Wheel Diameter


Tire diameter in inches

Then go to the end of the page and punch in your info for gear ratio
"this is approx doubt the factory tach is "right on"""

Let me know now I'M curious..... ;)

well...i couldn't find that number you told me to look for on the tire but i assumed it was 27. i drove my car in 3 since my car automatically goes into overdrive in D and my rpm were at 2400 at 60 mph. i put those numbers into the calculator...(27 diameter 2400RPM and 60MPH) and it came up with 3.21...which would mean i have the 3.23 however i dont know if driving in 3 is the reason. what do you think?

then again when i assumed the tire diameter was 23...i came up wth 2.74 so yea this is a pain in my ass

your 98 has 245/50/16 stock, stock tire size is about 25.5 inches,

and you can hold your tranny in 1st(you said there is a 1 on your shifter), indicating that you indeed have the 3.23 gear out back

then again when i assumed the tire diameter was 23...i came up wth 2.74 so yea this is a pain in my ass


Pain in the ass? You can also pull the diff cover off and count the ring and pinion gear teeth and divide . Or look on the axle housing tubes and scrap all the rust of and look for the axel number . Trust me this is a LOT less messy (P.S. you could also pull up the drivers side back seat cusion and under it SHOULD be a build sheet telling you EVERYTHING you would want to know about the car All options) I think that where they usally are....

well...i couldn't find that number you told me to look for on the tire

It has to be on the sidewall small or big black letters right after the tire makers name like P275/185/R16 -unless you have hit ALOT of curbs. ;)

alright thanks alot

so the fact that i can hold my tran in 1str means i have the 3.23gear and thus the 3 series carrier?

well never mind i realized im an idiot and just called the dealership i got my trans from and they found out with the vin number...unfortunately i have the 2.73 with the 2 series carrier....oh wel ill just buy a 3.73 that fits with 2-series...thanks anyway though

I know I keep saying this but am I dreaming when I say that there is a RPO code on the inside of the drivers door jamb that tells what axle you have? I need to look and see what mine has actually. I know for sure it is posi.
Rob

if i have a 2 series carrier on my 98 trans am does that mean i dont have posi rear...cuz both my wheels spin when i light them up

if i have a 2 series carrier on my 98 trans am does that mean i dont have posi rear...cuz both my wheels spin when i light them up
Two black marks from tires = posi I belive all ta's came w/ posi- Carrier size or gear size have nothing to do with it being posi. and the correct term is 'Limited slip' I belive...

Here are the Axel RPO codes for the 4 Gen Cars.

GU2 is 2.73 Ratio
GU4 is 3.08 Ratio
GU5 is 3.23 Ratio
GU6 is 3.42 Ratio (6 speed only)
G80 indicates you car has Posi

The RPO Code lists are located in the Glove box on 93-95 Camaro /firebirds and on the drivers door on the 96-02 Camaro/Firebirds.